It is known that modern aircraft, in particular civil transport planes, comprise movable spoiler flaps, also referred to as “air brakes”. Such spoiler flaps constitute aerodynamic control surfaces and they are generally installed in the upper face of the wings, behind their box structure and in front of the trailing edge flaps on which their own trailing edges rest.
Under the action of means of actuation, for example hydraulic, electrical or mechanical rams, themselves controlled from a lever actuated by the pilot of the aircraft, said spoiler flaps can take:                either a retracted position, for which they are housed in the upper face of the corresponding wing while ensuring the aerodynamic continuity of said upper face;        or one or other of several deployed positions, for which they protrude with respect to the upper face of the corresponding wing, while being inclined with respect to said upper face.        
Thus, in retracted position, said spoiler flaps blend into the aerodynamic profile of the upper face of the wings of the aircraft. On the other hand, for each of the deployed positions—each of which is associated with a specific function and is defined by a value of angle of deflection with respect to the corresponding upper face—said spoiler flaps cause a decrease in lift and an increase in drag whose amplitudes depend on said angle of deflection and on the surface area of said spoiler flaps and which may be used for various purposes such as:                reduction in the speed of the aircraft during the phases of landing and, possibly, of interruption of take-off;        reduction in the speed of the aircraft in flight or increase in the descent slope of said aircraft;        bearing down on the aircraft on the ground to improve braking during the phases of landing or of interruption of take-off;        in-flight control of the roll of the aircraft by acting asymmetrically on the spoiler flaps of the two wings;        generation of a yawing moment by asymmetric action on the spoiler flaps of the two wings helping to counter the effects of a fault with an engine during take-off; or        aid in decreasing the fixed-end moment where the wing is built into the fuselage, at high load factors (maneuvers, gusts of wind) by modifying the distribution of the lift along the wings.        
Thus, the functions performed by the spoiler flaps are varied.
However, since the deployment of said spoiler flaps causes a loss of lift, their use in flight is accompanied by a reduction in the flight domain of said aircraft. Specifically, if the pilot wishes to compensate at least in part for this loss of lift so as to maintain safety and flight comfort, he must either increase the incidence of the aircraft, or accelerate the latter. If the aircraft were flying at an incidence close to the maximum incidence, the pilot has no other choice than to accelerate. In this case, the deployment of the spoiler flaps is therefore accompanied by a reduction in the flight domain, as far as speeds are concerned. The same goes for the turning capability, that is to say maneuverability, of the aircraft. Specifically, a turn requires an increase in lift, and hence in the incidence, of an aircraft. Since the deployment of the spoiler flaps limits the available incidence, it simultaneously limits the maneuverability of the aircraft.